U.S. Pat. No. 5,013,324 to Zolman et al. discloses a prosthetic implant which includes a discrete, circumferential porous pad mounted directly onto the stem of an implant. The pad includes a first end and a second end such that when the pad is mounted on the stem, the first end and second end of the pad face each other and are flush with one another. This prior art device of U.S. Pat. No. 5,013,324 is shown in FIGS. 1-2 of the present application. The first end and second end of the prior art porous pad shown in FIG. 2 include straight edges which abut each other as shown in FIG. 1 to form a straight seam therebetween.
It has been discovered that over time particulate matter or wear debris may be generated from a prosthetic implant device. This wear debris could travel along this seam in which the two ends of the pad are merely aligned with or abutted against each other. This wear debris could cause bone lysis.